Apparatus for igniting oil-bearing formations



Jan. 30, 1968 MCARTHUR 3,366,180

APPARATUS FOR lGNITING OIL-BEARING FORMATIONS Filed DeC. 6, 1965 PWTTK AIR `GAS

JOE l.. Mc ARTHUR lNVENTOR.

ATTORNEY.

United States Patent O 3,366,180 APPARATUS FOR IGNITING OIL-BEARING FORMATIONS .loe L. McArthur, Pampa, Tex., assigner to Pan American Petroleum Corporation, Tulsa, Okla., a corporation of Delaware Filed Dec. 6, 1965, Ser. No. 511,639 4 Claims. (Cl. 166-58) ABSTRACT F THE DISCLOSURE One method of igniting a combustion well is to lower a receptacle containing triethylborane, break it at bottom, and contact it with air. To prevent a premature explosion, the reactant is encapsulated, placed in a burner assembly, and lowered to bottom by wire line. A pin is then sheared by a jarring action, and the reactant liberated and contacted with air.

The present invention relates to an apparatus suitable for heating or effecting ignition of a hydrocarbon-containing formation penetrated by a well. More particularly it is concerned with a novel heater or igniter employing a pyrophoric material to ignite a .fuel-oxygen containing gas mixture, the composition of which is controlled so as to regulate the final adiabatic mixture temperature of the oxidation or combustion products and excess air.

Briefly, my invention comprises a heater apparatus that can be lowered on a wire line into a well, said apparatus carrying in the lower end thereof a pyrophoric substance in encapsulated form, together with means for liberating said substance from its container at the time desired.

Many methods have been employed in the prior art for applying heat to hydrocarbon-containing formations such as, for example, by electrical means, by injecting heat transfer agents such as steam, hot oil, etc., into the well and by burning natural gas in the well bore. One of the principal difficulties has been that in the course of heating the formation to ignition temperature, the casing or screen as well as any other equipment in the vicinity of the heated zone is damaged by the excessive temperatures generated. In fact, the temperatures produced have been so high that the burner itself was considered an expendable item. The electric heaters employed for ignition and for paraffin deposition control have been subjected to` a number of practical problems, including shorting out; in some instances, such equipment has been lost in the hole and is extremely idiflicult to recover.

Also, in U.S. 3,223,165, a wire line operated heater is disclosed which employs pyrophoric materials to ignite an air-gas mixture. On combustion of the mixture the igniter is withdrawn. In operating this apparatus, gas is introduced down the tubing and air down the annulus between the tubing and casing. When all air in the tubing has been purged with gas, a lubricator with a side opening is flushed out with nitrogen and the pyrophoric chemical added to an open container which may or may not be filled with crushed charcoal. The igniter is then lowered to a level just above the bottom of the tubing. Gas ow is halted and the ow of air down the annulus is continued to purge the wellbore below the lower end of the tubing of a combustible mixture. The igniter, with the open container of pyrophoric material is then lowered onto a seating ring after which gas flow through the tubing is resumed. As soon as the pyrophoric substance is contacted with air, it ignites and in turn ignites the cornbustible air-gas mixture with which it is in contact. Thereafter the igniter tube is withdrawn.

While this type of apparatus marks a decided advance in the technique of formation heating and ignition, it can ICC be hazardous. First of all, in dealing with a pyrophoric substance, precautions must be taken to avoid premature ignition thereof. This necessitates a lubricator or equivalent apparatus which renders such procedure more complex and time-consuming. Also, if an air-gas mixture is inadvertently produced in the tubing at the wrong time, an explosion can occur. In one such case this did happen and the injection well was ruined.

Accordingly, it is an object of my invention to provide a heating apparatus adapted to operate on air-gas mixtures which are ignited by a means of pyrophoric substance wherein the latter is protected from a combustible mixture or a combustion supporting atmosphere until the operator is actually ready to ignite the heater. It is another object of my invention to protect said substance from burning prematurely by placing it in a suitable capsule or closed container that can be opened or broken.

In the drawings:

FIGURE 1 is an elevational view primarily in section showing the heater as it is lowered into the well.

FIGURE 2 likewise is an elevational view primarily in section in which the burner is landed at the desired level in the well and is ready to ignite a combustible mixture in Contact therewith.

Referring again to FIGURE l, a cased well 2 penetrates an oil-bearing zone 4. Tubing string 6 carries heat shield 8 having inner refractory lining 9, said shield being held on the lower end of said string by means of threaded coupling 10. Heat shield 8 is held in position by means of supports 11, the opposite ends of which are anchored to the base of neck 13. The inner portion of the apparatus is lowered down tubing string 6 by means of wire line 12 atixed to sinker bar 14 having a removable head 16 through which the wire is run and secured to sinker bar 14. At the lower end of sinker bar 14 is a jar assembly composed of shaft 18 and head 2li. When the equipment is being lowered on wire line 12, the jar assembly and perforated housing 22 are in the position as shown. Shaft 18 of the jar assembly is held in place by means of wire 19 while the heater is being lowered into position. Housing 22 has perforations 24 near the upper end thereof to accommodate the ow of gas into the burning zone once the heater is in operation. At the lower end of the housing are larger holes 26 through which the encapsulated pyrophoric material in container 28 is inserted and from which gas entering perforating housing 22 flows. About midway on the exterior of housing 22 is an annular shoulder 30 encircling said housing which is adapted to hold the entire assembly in place when the latter comes to rest on seating ring 32 carried in the lower end of neck 13.

FIGURE 2 shows the equipment in position for operation, capsule 28 having been broken or fractured by shearing wire 19 with the weight of sinker bar 14 permitting piercing head 20 to penetrate the capsule.

In operation, capsule 28 is placed in the apparatus through holes 26 and the assembly lowered on wire line 2 to within 20 to 30 feet of seating ring 32. Tubing string 6, when the apparatus is lowered down it, is filled, for example, with natural gas. Simultaneously air is injected down annulus 34 and mixes with gas within heat shield 8. When said assembly has been lowered to the above-mentioned level, gas injection is discontinued momentarily, thus permitting the space in the immediate vicinity of the heater to be purged of gas. The assembly is then lowered to seat accordingly on ring 32 and sinker bar 14 is permitted to drop and rest on the top of housing 22, resulting in breaking capsule 28 with piercing head 20 of the jar assembly. The pyrophoric material in capsule 28 on contact with air ignites and burns for a period generally of about l0 to 15 minutes. Immediately after capsule 28 is fractured, gas injection down tubing string 6 is resumed,

owing through holes 24 and 26 and then contacting air which tlows down annulus 34 and then through spaces between supports 11 to form a combustible mixture within heat shield 8. Successful ignition is generally evidenced by an immediate drop in air rate and a rise in injection pressure.

After the desired amount of heat has been injected, tubing string 6 should be purged free of natural gas. This operation is conveniently carried out by introducing about two 220 s.c.f. cylinders of nitrogen into the suction gas compressor, followed by opening the suction to air. The time required for the nitrogen to reach the burner should be computed. The burner can generally be observed to go out as the result of smooth action of the air rate and pressure pens on the air meter at approximately the calculated time.

Refractory cement 9 may be chosen from a wide range of materials such as the high alumina cements which generally contain from 35 to 40 percent A1203, 30 to 35 percent CaO, 10 to 15 percent Fe2O3, and a combined percentage of silicon and magnesium oxides of from to 10 percent. Any castable refractory material capable of withstanding temperatures of at least about 3000o F. is suitable. One particular refractory I have found useful for this purpose is Alfrax refractory cement manufactured by the Carborundum Company, Perth Amboy, NJ. This is a castable material which can be applied as a mud after mixing with water. The refractory sets within about 24 hours and generally tiring before use is unnecessary.

Substantially any pyrophoric material, liquid or solid, is satisfactory for my purpose. Thus, in addition to alkyl boranes, typified by triethylborane, there may be mentioned pyrophoric metals, phosphorous, aluminum borohydride, aluminum alkyls, pentaborane, and the like.

The capsules employed for carrying the pyrophoric material in accordance with my invention may be constructed of any of a number of materials, such as, for example, glass, plastic, ceramic metal, etc. Typical of the capsule designs suitable for use are the expendable containers used to hold jet perforating charges. These capsules should be sufficient in size to hold a quantity of pyrophoric material that will burn in the presence of air for a period of at least to 15 minutes. Usually a container having a volume of .from about 2 to about 8 cubic inches will hold enough of the pyrophoric substance to burn for the desired length of time.

While I have shown that these capsules can be broken by means of a suitable jar assembly, it will be apparent that numerous other means may be employed to accomplish this object, such as, for example, by attaching a K small piece of Primacord to the container and setting it off in a known manner.

I claim:

1. In a burner apparatus having an elongated, openended housing, a hollow, open-ended member extending part way into one end of said housing, spaced members about said one end holding said hollow member in alignment with the longitudinal axis of said housing and in substantially concentric relationship with said housing, the combination comprising a hollow, elongated, perforated, detachably mounted member within said hollow member and adapted to carry therewithin a closed container of a pyrophoric material, reciprocating means within said perforated member for opening the contents of said container to the surrounding atmosphere, a driving means adapted to force said reciprocating means in a downwardly direction, and frangible means holding said reciprocating means out of contact with said container until broken by the action of said driving means 0n said reciprocating means.

2. The burner apparatus of claim 1 wherein the driving means is a sinker bar affixed to the upper extremity of said reciprocating means.

3. The burner apparatus of claim 1 wherein said frangible means is a shear pin running through said reciprocating means, the opposite ends of said pin being held by said perforated member.

4. In a burner apparatus the combination comprising an elongated hollow, perforated member adapted to carry therewithin a closed container of a pyrophoric material, reciprocating means within said perforated member for opening the contents of said container to the surrounding atmosphere, a driving means adapted to force said reciprocating means in a downwardly direction, and frangible means holding said reciprocating means out of contact with said container until broken by the action of said driving means on said reciprocating means.

References Cited UNITED STATES PATENTS 2,366,373 1/1945 Voorhees 166--38 X 3,172,472 3/1965 Smith 166-38 3,179,169 4/1965 Cline 166-38 3,195,637 7/1965 Wayte 166-58 3,205,947 9/1965 Parker 166-38 3,223,165 12/1965 Hujsak 166-38 ERNEST R. PURSER, Primary Examiner.

NILE C. BYERS, JR., Examiner. 

